WASHINGTON, D.C. — President Barack Obama has ordered a full review of foreign-based digital attacks that U.S. intelligence agencies say were aimed at influencing this year’s presidential election, a top White House official said Friday.

The disclosure came after President-elect Donald Trump again dismissed a blunt U.S. intelligence assessment that concluded senior Russian authorities had authorized the digital theft of emails from Democratic Party officials and Hillary Clinton’s campaign manager during the campaign.

Trump has repeatedly praised Russian President Vladimir Putin, raising concerns among intelligence experts that he is ignoring potential threats to U.S. national security.

Officials said the cyberattacks were the first known attempt to try to interfere with a U.S. election to discredit American democracy or a specific candidate, a clear escalation of traditional cyberespionage.

“We may be crossing into a new threshold and it’s incumbent upon us to take stock of that,” said Lisa Monaco, White House counterterrorism and Homeland Security adviser.

U.S. officials will be “very attentive to not disclosing sources and methods that may impede our ability to identify and attribute malicious actors in the future,” said Monaco, who disclosed the intelligence review at a breakfast arranged by The Christian Science Monitor.

The classified inquiry will focus on what happened and “lessons learned,” Monaco said, and will be completed before Obama leaves office on Jan. 20.

It will be shared with “a range of stakeholders,” she said, including members of Congress, but she did not commit to making it public.

Trump has repeatedly derided claims that Russian authorities played a role in the hacks and the subsequent release of thousands of emails from Democratic National Committee staff accounts and the private account of John Podesta, chairman of Clinton’s campaign.

In an interview with Time magazine published this week, Trump said he didn’t believe Putin’s government hacked the Democrats’ computers to help his candidacy.

“I don’t believe they interfered,” Trump said. “That became a laughing point — not a talking point — a laughing point,” he said, implying that the intelligence assessments were politically motivated.

The hacking, he said, “could be Russia. It could be China. And it could be some guy in New Jersey.”

Trump has rejected a joint statement issued Oct. 7 by Secretary of Homeland Security Jeh Johnson and Director of National Intelligence James R. Clapper, who leads the 17 U.S. intelligence agencies.

The U.S. intelligence community “is confident that the Russian Government directed the recent compromises of e-mails from U.S. persons and institutions, including from U.S. political organizations,” the statement said.

“We believe, based on the scope and sensitivity of these efforts, that only Russia’s senior-most officials could have authorized these activities,” it added.

The statement also said a Russian company apparently had probed computerized voting systems used by individual states, but it stopped short of blaming the Russian government.

Using an emergency communications system set up to prevent an accidental nuclear war, the White House warned Putin’s government to stop the cyberattacks and not to interfere with voting systems, according to later reports.

No further disruptions were reported, U.S. officials said. Russia’s government has denied any role in the hacks or in trying to subvert the U.S. election.

Several senior Republicans in Congress have broken with Trump on the issue, saying they are convinced by the intelligence.

Sen. John McCain of Arizona, the chairman of the Senate Armed Services Committee, said “there’s very little doubt” that Putin’s government sought to interfere with the election.

“The problem with hacking is that if they’re able to disrupt elections then it’s a national security issue, obviously,” he said in an interview.

Sen. Lindsey Graham, R-S.C., said the Senate Armed Services subcommittee that he heads will investigate Russian hacking when Congress returns next year.

Rep. Devin Nunes, R-Calif., chairman of the House Intelligence Committee, said that Russian cyberattacks were “no surprise” and that the Obama administration had ignored calls to take more forceful action against Russia.

“The intelligence community has repeatedly failed to anticipate Putin’s hostile actions,” Nunes said. “It appears, however, that after eight years the administration has suddenly awoken to the threat.”

Trump’s unwillingness to accept assessments from career intelligence officials is highly unusual. So is his refusal to accept more than a handful of classified intelligence briefings since his upset victory a month ago.

Given Trump’s “disturbing refusal to listen to our intelligence community and accept that the hacking was orchestrated by the Kremlin, there is an added urgency … for a thorough review,” said Rep. Adam B. Schiff of California, the top Democrat on the House Intelligence Committee.

Sen. Dianne Feinstein of California, the top Democrat on the Senate intelligence committee, said that she had become increasingly concerned over the last six months about Russian government efforts “to influence our election” and agrees that “only the senior-most government officials in Russia could have ordered this effort.”